Thank for the advice and link, Meg, but your are overly paranoid RE CleanMyMac 2. For fear of hijacking this tread (FCP + Yosamite) I will be very brief. (And, no, I do not work for MacPaw and am generally not a fan of their software.)
I've been a Mac-man since '84, and still have my 512k Mac SE (Yes, I still have it working). Now I am a Certified Computer Forensic Examiner and know very very well what goes on under the hood of OS X, am very familiar with the directory corruption that seems so persistent in the HFS+ file system, the relatively unstable permissions and all the crap that doesn't get cleaned out or managed "automatically" or at all by OS X. I don't need Arabic, French, Spanish, Danish or any other of the multitude of language iterations of OS X and/or other Apple software that unnecessarily sapping gigabytes of space on my machine. If I drag an App to the Trash there can be a multitude of extensions, drivers, settings/plists files and other junk that does NOT get removed with it... and if the average user discovers how to get into their relatively hidden Users/(Profile)/Library and try to remove stuff manually they are very likely to screw up their OS or break their other software. I have tested CleanMyMac 2 in a lab environment and, while the original was kind of screwy and less effective, CleanMyMac 2, does an excellent job of getting rid of totally unnecessary, disk-bloating CRAP from your drive and does it in a manner that is way more efficient and reliable than trying to do it manually. I've never had a negative experience with CMM2 and have found it to be no more difficult to remove manually than any of a bunch of other software.
While it does nothing to correct permissions errors or fix directory issues (sorry OS X Disk Utility ***** at that), I've found it to do an excellent job at locating and cleaning out all the stuff that OS X simply does not do on its own and does result in a more efficient, slightly faster-running machine.
Again, Meg, I appreciate your trying to help me out and provide caution regarding "cleaning" software. I, myself remain generally dubious about other products from MacPaw (particularly Gemini). It is certainly your right to avoid all of it and even Troll my feedback regarding CMM2. But lab results don't lie and my experience has consistently shown CleanMyMac 2 to be useful and non-destructive to my system and/or other software.
...... And it was an effective utility I used to get my FCP 7 to work again.